/*
chacha-merged.c version 20080118
D. J. Bernstein
Public domain.
*/

#include "ecrypt_sync.h"
#include "ecrypt_portable.h"

#define ROTATE(v, c) (ROTL32(v, c))
#define XOR(v, w) ((v) ^ (w))
#define PLUS(v, w) (U32V((v) + (w)))
#define PLUSONE(v) (PLUS((v), 1))

#define QUARTERROUND(a, b, c, d) \
    a = PLUS(a, b);              \
    d = ROTATE(XOR(d, a), 16);   \
    c = PLUS(c, d);              \
    b = ROTATE(XOR(b, c), 12);   \
    a = PLUS(a, b);              \
    d = ROTATE(XOR(d, a), 8);    \
    c = PLUS(c, d);              \
    b = ROTATE(XOR(b, c), 7);

void ECRYPT_init(void) {
    return;
}

static const char sigma[16] = "expand 32-byte k";
static const char tau[16] = "expand 16-byte k";

void ECRYPT_keysetup(ECRYPT_ctx* x, const u8* k, u32 kbits, u32 ivbits) {
    (void)ivbits;
    const char* constants = (const char*)0;

    x->input[4] = U8TO32_LITTLE(k + 0);
    x->input[5] = U8TO32_LITTLE(k + 4);
    x->input[6] = U8TO32_LITTLE(k + 8);
    x->input[7] = U8TO32_LITTLE(k + 12);
    if(kbits == 256) { /* recommended */
        k += 16;
        constants = sigma;
    } else { /* kbits == 128 */
        constants = tau;
    }
    x->input[8] = U8TO32_LITTLE(k + 0);
    x->input[9] = U8TO32_LITTLE(k + 4);
    x->input[10] = U8TO32_LITTLE(k + 8);
    x->input[11] = U8TO32_LITTLE(k + 12);
    x->input[0] = U8TO32_LITTLE(constants + 0);
    x->input[1] = U8TO32_LITTLE(constants + 4);
    x->input[2] = U8TO32_LITTLE(constants + 8);
    x->input[3] = U8TO32_LITTLE(constants + 12);
}

void ECRYPT_ivsetup(ECRYPT_ctx* x, const u8* iv) {
    x->input[12] = 0;
    x->input[13] = 0;
    x->input[14] = U8TO32_LITTLE(iv + 0);
    x->input[15] = U8TO32_LITTLE(iv + 4);
}

void ECRYPT_ctrsetup(ECRYPT_ctx* x, const u8* ctr) {
    x->input[12] = U8TO32_LITTLE(ctr + 0);
    x->input[13] = U8TO32_LITTLE(ctr + 4);
}

void ECRYPT_encrypt_bytes(ECRYPT_ctx* x, const u8* m, u8* c, u32 bytes) {
    u32 x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0, x8 = 0, x9 = 0, x10 = 0,
        x11 = 0, x12 = 0, x13 = 0, x14 = 0, x15 = 0;
    u32 j0 = 0, j1 = 0, j2 = 0, j3 = 0, j4 = 0, j5 = 0, j6 = 0, j7 = 0, j8 = 0, j9 = 0, j10 = 0,
        j11 = 0, j12 = 0, j13 = 0, j14 = 0, j15 = 0;
    u8* ctarget = 0;
    u8 tmp[64] = {0};
    int i = 0;

    if(!bytes) return;

    j0 = x->input[0];
    j1 = x->input[1];
    j2 = x->input[2];
    j3 = x->input[3];
    j4 = x->input[4];
    j5 = x->input[5];
    j6 = x->input[6];
    j7 = x->input[7];
    j8 = x->input[8];
    j9 = x->input[9];
    j10 = x->input[10];
    j11 = x->input[11];
    j12 = x->input[12];
    j13 = x->input[13];
    j14 = x->input[14];
    j15 = x->input[15];

    for(;;) {
        if(bytes < 64) {
            for(i = 0; i < (int)bytes; ++i) tmp[i] = m[i];
            m = tmp;
            ctarget = c;
            c = tmp;
        }
        x0 = j0;
        x1 = j1;
        x2 = j2;
        x3 = j3;
        x4 = j4;
        x5 = j5;
        x6 = j6;
        x7 = j7;
        x8 = j8;
        x9 = j9;
        x10 = j10;
        x11 = j11;
        x12 = j12;
        x13 = j13;
        x14 = j14;
        x15 = j15;
        for(i = 20; i > 0; i -= 2) {
            QUARTERROUND(x0, x4, x8, x12)
            QUARTERROUND(x1, x5, x9, x13)
            QUARTERROUND(x2, x6, x10, x14)
            QUARTERROUND(x3, x7, x11, x15)
            QUARTERROUND(x0, x5, x10, x15)
            QUARTERROUND(x1, x6, x11, x12)
            QUARTERROUND(x2, x7, x8, x13)
            QUARTERROUND(x3, x4, x9, x14)
        }
        x0 = PLUS(x0, j0);
        x1 = PLUS(x1, j1);
        x2 = PLUS(x2, j2);
        x3 = PLUS(x3, j3);
        x4 = PLUS(x4, j4);
        x5 = PLUS(x5, j5);
        x6 = PLUS(x6, j6);
        x7 = PLUS(x7, j7);
        x8 = PLUS(x8, j8);
        x9 = PLUS(x9, j9);
        x10 = PLUS(x10, j10);
        x11 = PLUS(x11, j11);
        x12 = PLUS(x12, j12);
        x13 = PLUS(x13, j13);
        x14 = PLUS(x14, j14);
        x15 = PLUS(x15, j15);

        x0 = XOR(x0, U8TO32_LITTLE(m + 0));
        x1 = XOR(x1, U8TO32_LITTLE(m + 4));
        x2 = XOR(x2, U8TO32_LITTLE(m + 8));
        x3 = XOR(x3, U8TO32_LITTLE(m + 12));
        x4 = XOR(x4, U8TO32_LITTLE(m + 16));
        x5 = XOR(x5, U8TO32_LITTLE(m + 20));
        x6 = XOR(x6, U8TO32_LITTLE(m + 24));
        x7 = XOR(x7, U8TO32_LITTLE(m + 28));
        x8 = XOR(x8, U8TO32_LITTLE(m + 32));
        x9 = XOR(x9, U8TO32_LITTLE(m + 36));
        x10 = XOR(x10, U8TO32_LITTLE(m + 40));
        x11 = XOR(x11, U8TO32_LITTLE(m + 44));
        x12 = XOR(x12, U8TO32_LITTLE(m + 48));
        x13 = XOR(x13, U8TO32_LITTLE(m + 52));
        x14 = XOR(x14, U8TO32_LITTLE(m + 56));
        x15 = XOR(x15, U8TO32_LITTLE(m + 60));

        j12 = PLUSONE(j12);
        if(!j12) {
            j13 = PLUSONE(j13);
            /* stopping at 2^70 bytes per nonce is user's responsibility */
        }

        U32TO8_LITTLE(c + 0, x0);
        U32TO8_LITTLE(c + 4, x1);
        U32TO8_LITTLE(c + 8, x2);
        U32TO8_LITTLE(c + 12, x3);
        U32TO8_LITTLE(c + 16, x4);
        U32TO8_LITTLE(c + 20, x5);
        U32TO8_LITTLE(c + 24, x6);
        U32TO8_LITTLE(c + 28, x7);
        U32TO8_LITTLE(c + 32, x8);
        U32TO8_LITTLE(c + 36, x9);
        U32TO8_LITTLE(c + 40, x10);
        U32TO8_LITTLE(c + 44, x11);
        U32TO8_LITTLE(c + 48, x12);
        U32TO8_LITTLE(c + 52, x13);
        U32TO8_LITTLE(c + 56, x14);
        U32TO8_LITTLE(c + 60, x15);

        if(bytes <= 64) {
            if(bytes < 64) {
                for(i = 0; i < (int)bytes; ++i) ctarget[i] = c[i];
            }
            x->input[12] = j12;
            x->input[13] = j13;
            return;
        }
        bytes -= 64;
        c += 64;
        m += 64;
    }
}

void ECRYPT_decrypt_bytes(ECRYPT_ctx* x, const u8* c, u8* m, u32 bytes) {
    ECRYPT_encrypt_bytes(x, c, m, bytes);
}

void ECRYPT_keystream_bytes(ECRYPT_ctx* x, u8* stream, u32 bytes) {
    u32 i = 0;
    for(i = 0; i < bytes; ++i) stream[i] = 0;
    ECRYPT_encrypt_bytes(x, stream, stream, bytes);
}

void hchacha20(ECRYPT_ctx* x, u8* c) {
    u32 x0 = 0, x1 = 0, x2 = 0, x3 = 0, x4 = 0, x5 = 0, x6 = 0, x7 = 0, x8 = 0, x9 = 0, x10 = 0,
        x11 = 0, x12 = 0, x13 = 0, x14 = 0, x15 = 0;
    int i = 0;

    x0 = x->input[0];
    x1 = x->input[1];
    x2 = x->input[2];
    x3 = x->input[3];
    x4 = x->input[4];
    x5 = x->input[5];
    x6 = x->input[6];
    x7 = x->input[7];
    x8 = x->input[8];
    x9 = x->input[9];
    x10 = x->input[10];
    x11 = x->input[11];
    x12 = x->input[12];
    x13 = x->input[13];
    x14 = x->input[14];
    x15 = x->input[15];

    for(i = 20; i > 0; i -= 2) {
        QUARTERROUND(x0, x4, x8, x12)
        QUARTERROUND(x1, x5, x9, x13)
        QUARTERROUND(x2, x6, x10, x14)
        QUARTERROUND(x3, x7, x11, x15)
        QUARTERROUND(x0, x5, x10, x15)
        QUARTERROUND(x1, x6, x11, x12)
        QUARTERROUND(x2, x7, x8, x13)
        QUARTERROUND(x3, x4, x9, x14)
    }

    U32TO8_LITTLE(c + 0, x0);
    U32TO8_LITTLE(c + 4, x1);
    U32TO8_LITTLE(c + 8, x2);
    U32TO8_LITTLE(c + 12, x3);
    U32TO8_LITTLE(c + 16, x12);
    U32TO8_LITTLE(c + 20, x13);
    U32TO8_LITTLE(c + 24, x14);
    U32TO8_LITTLE(c + 28, x15);
}
